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From Greg Turnquist <>
Subject Working on a variant of McastService
Date Mon, 17 Dec 2012 21:08:47 GMT
I ran into issues using McastService on my own setup. Took me awhile to
figure out I was colliding with another instance of tomcat running
elsewhere, sharing the same multicast port. I have started thinking that if
I wrote a different version of McastService that embedded some sort of
logical cluster name, I could detect collisions with other,
differently-named clusters and write some log messages to cause things to
fail faster. In the process, I found that code like
org.apache.catalina.tribes.membership.MessageImpl is highly cohesive. There
are a lot of hard-coded downcasts to the concrete implementation instead of
relying on interfaces.

I was planning to work on a potential patch to submit here that would
involve refactoring things so there are no down casts to MessageImpl and
also possibly removing the static calls as well. With that, it should
become easier to code alternative protocols, including my own that I need
(and hope to contribute back), as well as supporting others that want to
design a pluggable message protocol between their own instances.

If anyone has an opinion on this, please let me know. I'll update this list
when I have a patch to consider.

Greg Turnquist (

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